1. Field of the Invention
The present invention relates to a method for managing the connection of digital devices connected to a digital interface through the digital interface, and more particularly, to a method for managing a digital interface connection which, when a point-to-point connection is established among digital devices connected through a digital interface, such as an IEEE 1394, enables the concerned device of the point-to-point connection to release this connection.
2. Description of the Related Art
A plurality of digital devices can be interconnected through a digital interface which conforms to an interface standard such as the IEEE 1394 standard. A connection managing method between those digital devices is described in the International Electrotechnical Commission (IEC) 61883 standard. According to the IEC 61883 standard, input and output plugs are defined for each digital device as the entry of an incoming bit stream and the exit of an outgoing bit stream, respectively. Further, the input and output plugs are controlled by managing registers such as an output master plug register (oMPR), an output plug control register (oPCR), an input master plug register (iMPR), and an input plug control register (iPCR), so that a connection between digital devices can be managed.
A point-to-point connection, which is a connection made between such digital devices, consists of an output plug, an input plug, and a channel therebetween. The connection is defined such that an arbitrary device can establish or overlay the connection and that only a device which establishes the connection can break the connection. Establishment or release of the point-to-point connection is performed by managing registers such as oMPR, oPCR, iMPR, and iPCR.
FIG. 1 is a diagram for explaining a conventional method for managing connections.
FIG. 2 shows the connection related fields of oPCR and iPCR used in the IEC 61883 standard. Referring to FIG. 1, a point-to-point connection is established among a DVCR 10, a first DTV 12, and a second DTV 14 by an IEEE 1394 interface. Referring to FIG. 2, in devices utilizing the conventional method for managing connections, an output plug control register oPCR shown in (a) and an input plug control register iPCR shown in (b) include the connection related fields P-2-Pcnt and nCh, respectively. For example, if devices having the plug control registers are point-to-point connected, the content of oPCR of DVCR 10 is oPCR.P-2-P_Connection_Counter(P-2-Pcnt)=1, oPCR. Channel_Number (nCh)=33. The content of iPCR of first DTV 12 is iPCR.P-2-P_Connection_Counter(P-2-Pcnt)=1, iPCR.Channel_Number(nCh)=33. Furthermore, if the operation of iPCR and oPCR is performed successfully, a point-to-point connection of DVCR 10 and first DTV 12 is established. The IEEE 1394 modules of DVCR 10 and first DTV 12 are controlled by connection establishment information denoting the connection establishment state of the point-to-point connection, thereby allowing first DTV 12 to receive and see the output content of DVCR 10.
When a connection is established between DVCR 10 and first DTV as described above, if second DTV 14 is to monitor the output content of DVCR 10, which is a sink device, second DTV 14 attempts to establish a point-to-point connection or broadcast-in connection with DVCR 10 by overlaying the connection on the already established point-to-point connection between DVCR 10 and first DTV 12. In the case where a point-to-point connection is overlaid and established between second DTV 14 and DVCR 10, the content of oPCR of DVCR 10 is oPCR.P-2-P_Connection_Counter(P-2-Pcnt)=2, oPCR.Channel_Number (nCh)=33. The content of iPCR of second DTV 12 is iPCR.P-2-P_Connection_Counter(P-2-Pcnt)=1, iPCR. Channel_Number (nCh)=33. Similarly, second DTV 14 controls its own IEEE 1394 module according to such information, which allows it to receive and see the output content of DVCR 10.
According to the IEC 61883 format, when a point-to-point connection is made, only a device which establishes the connection can release the connection. Thus, a point-to-point connection between DVCR 10 and first DTV 12 can be released by first DTV 12. If first DTV 12 releases the connection to DVCR 10, the content of oPCR of DVCR 10 is oPCR.P-2-P_Connection_Counter(P-2-Pcnt)=0, oPCR.Channel_Number (nCh)=33. The content of iPCR of first DTV 12 is iPCR.P-2-P_Connection_Counter(P-2-Pcnt)=0, iPCR. Channel_Number (nCh)=33.
If a device other than first DTV 12 attempts to break the connection between DVCR 10 and first DTV 12, the concerned devices do not allow such an attempt to be made because the attempt does not comply with the relevant format. Similarly, if a device other than second DTV 12 attempts to break the connection between DVCR 10 and second DTV 12, the concerned devices do not permit such attempt because the formats do not conform. These particulars are specified in IEC 61883, and all devices that desire to transmit audio-video contents as an isochronous bit stream must follow this format.
In the same context, according to a method for managing a digital interface connection according to the conventional art, for example, if a third party device establishes a point-to-point connection between first and second devices, the connection cannot be released by any device other than the third party device. In the above example, if first DTV 12, which is the concerned connected device, attempts to connect an input plug used in the connection to another device, because the input plug is already point-to-point connected to DVCR 10, first DTV 12 cannot break the connection so long as second DTV 14 does not do so. Eventually, first DTV 12 encounters a problem because a considerable part of its operation depends on the operation of second DTV 14. Furthermore, if second DTV 14 does not operate as desired by first DTV 12, second DTV 14 cannot perform its own desired operation.
For instance, it is assumed that when digital-video home system (D-VHS), DTV, and digital versatile disk (DVD) are connected to an IEEE 1394 network, a user converts D-VHS to a reproducing mode, and thus D-VHS establishes a point-to-point connection with DTV which is its own default display device. Furthermore, it is assumed that the user desires to view DVD in the middle of viewing D-VHS to select DVD as a source on the DTV screen by operating source select screen of the DTV. In this case, despite the fact that the user intends to break away from D-VHS content and to view the DVD content instead, the DTV cannot actually carry out such operation.
In order to perform the operation, the DTV must break a point-to point connection between its own input plug and D-VHS's output plug to thereafter establish a new connection between its own input plug and DVD's output plug. However, because the point-to-point connection is established by the D-VHS, the DTV has no authority to break the connection. Thus, the user's request to view DVD on the DTV screen is not satisfied. Therefore, a method for managing a digital interface connection according to the conventional art is inconvenient because the concerned connected device cannot break the connection.